You must declare your @exports using single-line ### comments:
### @export x ###
x = 5
This involves some ugly and not 100% correct low-level source hackery, making
some assumptions about the format that CoffeeScript generates.
Ha. Turns out that `.call(this)` is needed after all when a
CoffeeScript file is using "use strict".
(http://es5.github.io/#x15.3.4.4)
Thanks to pipedreambomb on stackoverflow for the bug report and to
user1737909 for the documentation reference.
